Recently, as the degree of integration of semiconductor device increases, the width of a line of its circuit pattern is presently in a deep sub-micron. In the case where a circuit pattern of a line width of a deep sub-micron, the internal atmosphere of the clean room must be controlled to a cleanness of a high level. Under these circumstances, the problem of organic materials adsorbed to the surface of a wafer is recently focused, in addition to the conventional problem that particle-like dust adheres to the surface of a wafer (for example, "Gaseous Contaminants and Present Situation of Counter-measures Taken to Eliminate It" by Fujii, Air Cleaning Vol. 32, No. 3, P43 (1994), Japan Society of Air Cleaning).
The inventors of the present invention conducted intensive studies on any factors which could give rise to a source of organic material in a clean room. The result indicated that aliphatic hydrocarbons, organic carboxylic acid esters, phenols, oxides of these materials and amines are generated in very small amount, from resin-made instruments such as wafer carriers and SMIF POD.
Further, according to other studies carried out by the same inventors, it was found that organic carboxylic acid esters, phenols and oxides of these materials are generated in very small amount from the sole (made of resin) of a conventional clean room shoe, as a so-called out-gas.
These organic materials are adsorbed to the surfaces of wafers eventually via air streams in the clean room, causing a variety of bad effects in the formation of a circuit pattern. For example, in the case where a gate oxide film is formed on the surface of a wafer while some organic materials are adsorbed on the surface of the wafer, the start of the growth of the film is delayed, the sheet resistance value of the film is decreased, and the surface of the film becomes rough in projections and recesses.